In the manufacture of steel-framed finished products, individual steel pieces are typically coated with a powder-coating material. As an example, the rails that form the floor rails for differing furniture pieces are powder coated. This involves delivering individual pieces of the steel frame along a conveyor belt and into a powder-coating apparatus. Induction heating is commonly used to preheat the steel pieces prior to powder coating. The overall process may also involve the use of a series of conveyor belts that deliver the steel pieces through induction, powder coating, and on to cooling.
One automated method of powder coating involves delivery of steel pieces along a continuous conveyor belt, or series of conveyor belts and/or roller conveyors. The steel pieces are preheated using induction heating coils and delivered at a consistent pace through a powder-coating apparatus. Having passed through the powder-coating apparatus, the steel pieces are transferred along the continuous conveyor belt for cooling and further processing. In some instances, the powder-coated pieces are manually hung in order to allow additional drying time for the powder-coating material. Using this method, the conveyor belt moves at a continuous pace, constantly moving pieces along the conveyor belt and through the powder-coating apparatus. Because the powder-coating method is continuous, and the pieces being delivered along the conveyor belt are the same or similar in length, the consistent speed of the conveyor belt is determined by the time needed to preheat and powder coat the similar-length pieces. The pieces of similar length are typically longer pieces of steel, which allows for a longer time to dry as the longer pieces exit the powder-coating apparatus.
One problem with current automated powder-coating methods is the application of powder coating to shorter-length steel pieces. Using a traditional, continuous conveyor belt method, longer and/or continuous-length steel pieces can wait a longer distance before needing to be contacted upon exiting the powder-coating apparatus, and therefore are able to dry before subsequent contact with the next portion of the conveyor belt. In other words, longer pieces travel a longer distance before contact is required. Conversely, shorter pieces are quicker to require contact upon exiting the powder-coating apparatus, and may not have enough time to sufficiently dry, or “cure,” before subsequent contact with the next portion of the conveyor belt. As such, freshly coated surfaces of shorter pieces may have more markings on the pieces from earlier contact with the conveyor belt.
Another problem with current powder-coating methods is the inability to handle inconsistent or varying lengths of steel pieces. For example, traditional powder-coating methods use continuous conveyor belts to transfer steel pieces, which does not take into account the length of the piece and the amount of time it takes the individual piece to complete each step of the process. Timing of the traditional powder-coating process is based on the continuous pace to powder coat longer-length pieces, regardless of the amount of time required for preheating with induction coils, the amount of time required to pass the steel piece through the powder-coating apparatus, and the amount of time required to dry the steel piece at the end of the process.
Accordingly, a need exists for an automated powder-coating method for coating variable lengths of steel pieces.